1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor device, and more particularly, to a method of fabricating a semiconductor device having an improved patterning technique.
2. Description of the Related Art
Memory cells storing data are typically coupled with a variety of devices. For example, in the case of a dynamic random access memory (DRAM) device, one memory cell includes one transistor and one capacitor. In particular, a DRAM device is made from a combination of memory cells and a variety of interconnection lines. This combination of memory cells and interconnection lines, requires steps for forming an insulating film or a conductive film on a substrate and properly patterning the insulating film or the conductive film. Besides DRAM devices, the above steps are likewise applied to other electronic appliances as well. For example, in the case of a liquid crystal display device (LCD) displaying an image using liquid crystals, a patterning step is needed for forming a thin film transistor, every pixel for the LCD and a variety of interconnection lines on a substrate.
In general, patterning for an etch target film is performed by etching and removing a selected portion of the etch target film. At this stage, an etch mask is formed on the etch target film such that a portion to be removed from the etch target film is exposed by the etch mask. Moreover, the etch mask can be formed by coating a photoresist film and exposing the coated photoresist film to light using a photomask. For example, when multiple layers are formed and patterned with different patterns from each other, photomasks corresponding to the number of the multiple layers used are required. A more detailed discussion regarding the patterning process will now be described with reference to the accompanying drawings.
FIGS. 1A to 1D are sectional views illustrating a process of patterning a film according to the conventional/related art.
Referring to FIG. 1A, a first etch target film 11 and a second etch target film 12 are formed on a substrate 10. The first and second etch target films 11 and 12 may be composed of a metal film, an insulating film and the like. A first photoresist pattern 21, which is used as an etch mask, is formed on the second etch target film 12. The first photoresist pattern 21 is formed by a conventional photolithography process, which includes coating a photoresist film on the second etch target film 12, thereby exposing the coated photoresist film to light passing through a photomask. The exposed portions are then removed.
Referring to FIG. 1B, exposed portions of the first etch target film 11 and the second etch target film 12 without the first photoresist pattern 21 thereon are then etched. After the exposed portions are etched, the first photoresist pattern 21 is then stripped. Subsequently, the first and second etch target films 11 and 12 are patterned to correspond to the first photoresist pattern.
Referring to FIG. 1C, a second photoresist pattern 22 is formed on the second etch target film 12. The second photoresist pattern can be also formed by a conventional photolithography process, which needs a separate photomask.
Referring to FIG. 1D, the second etch target film is etched using the second photoresist pattern 22. The second photoresist pattern 22 is then stripped. Next, the first etch target film 11 is patterned corresponding to the first photoresist pattern 21 and the second etch target film 12 is patterned corresponding to the second photoresist pattern 22. Consequently, two different photoresist patterns 21 and 22 are used to pattern the two etch target films 11 and 12, such that etch target films 11, 12 are each patterned differently. Moreover, the patterning of the two etch target films requires two photolithography processes to be performed. Further, since each of the photolithography processes uses a photomask, two photomasks are required for the above patterning process.
Thus, the above-described patterning method of the conventional/related art, requires a corresponding number of photolithography steps or processes to be performed for forming each photoresist pattern, thereby resulting in a complicated process when one seeks to form two or more photoresist patterns.
Accordingly, there is a need in the art for a more simplified method for fabricating a semiconductor device in comparison to the above-described methods of the conventional/related art. In particular, there is a need for a method for fabricating a semiconductor device, wherein two or more different photoresist patterns can be formed without performing a corresponding number of photolithography steps, thereby reducing the number of steps to be performed and also the number of photomasks to be used in comparison to the conventional/related art.